1. Field of the Invention
This invention relates generally to burglar alarm systems and more particularly to a self-contained monitor surveiling a predetermined space for an occurrence of an intrusion. The self-contained monitor may be remotely tested by a returning occupant to determine if an intrusion event has occurred in the predetermined space.
2. Description of Related Art
Burglar alarm systems comprising a self-contained monitor used to surveil a predetermined space having a remote controller transmitting an RF signal to control the self-contained monitor are well known in the prior art. In such systems, the monitor typically includes a primary power source, a motion sensor, a responder and a memory circuit. The motion sensor detects an unauthorized entry into the predetermined space causing the responder to sound an alarm and, at the same time, causing the memory circuit to record the occurrence of the intrusion. In certain prior art systems, the memory also records any interruption of primary power as an intrusion event. Before reentering the premises, a returning occupant activates the remote controller prompting a response from the self-contained monitor to determine if an intrusion event has occurred in order to determine whether it is safe to enter the premises.
Since the personal wellbeing of the returning occupant is at risk, it is essential that the self-contained monitor provides not only a reliable means by which to record an intrusion event but also a reliable means by which to remotely test whether an intrusion has, or has not, occurred. On one hand, it is extremely dangerous for a returning occupant to unwittingly confront an intruder. On the other, it is stressful, inconvenient and time consuming for the returning occupant to seek help mistakenly believing that an intrusion has occurred as a result of a false test report.
A self-contained monitor, employed by a returning occupant to remotely test for a remaining intruder, presents certain problems relating to its reporting accuracy and reliability because such monitors are often located in either apartments or homes where an intruder has the privacy and the time to gain control of the alarm system. In the privacy of an isolated premises, it is possible for the intruder to manipulate the self-contained monitor to purposely produce a false test report which causes the returning occupant to enter his or her premises unaware that the intruder remains therein. Further, in some instances, self-contained monitors are subject to primary power interruptions which may cause false test reports which result in the returning occupant needlessly seeking help. Finally, if the remote controller transmits a fixed frequency RF signal to control the self-contained monitor, the intruder can surreptitiously intercept the signal and easily determine its frequency by using what is known in the industry as a xe2x80x9ccode grabberxe2x80x9d. Subsequently, the intruder can gain control of the system by transmitting a duplicate signal causing the self-contained monitor to produce a false test report.
U.S. Pat. No. 6,137,405 which issued to the applicant of the present invention, William P. Carney, on Oct. 24, 2000 teaches an intrusion detection system including a self-contained monitor disposed to surveil a predetermined space for an intrusion event. Should an intrusion event occur during an occupant""s absence, the self-contained monitor not only sounds an alarm to frighten away the intruder but also records the occurrence of the event. Upon returning and before reentering the predetermined space, the occupant employs a remote controller to test the self-contained monitor prompting a response therefrom to determine if an intrusion event has occurred and whether or not it is safe to reenter. The self-contained monitor comprises a primary power source, an RF receiver circuit, a PIR motion detector, a memory circuit and a responder. The self-contained monitor is tuned to the remote controller by a tuning code set on a DIP switch in the monitor which matches a tuning code set on a DIP switch in the remote controller. The memory circuit taught by Carney includes a volatile memory circuit defining an armed state and a disarmed state and a nonvolatile memory circuit for storing the tuning code therein. The volatile memory circuit is armed and tested by a particular RF carrier signal transmitted by the remote controller to the self-contained monitor wherein it is qualified by the tuning code. Further, the self-contained monitor is disarmed by either sensing a power interruption or by the motion sensor detecting an intruder. In Carney, the volatile memory circuit can only be rearmed by a particular RF carrier signal qualified by the tuning code stored in the nonvolatile memory. Carney teaches that the tuning code set on the monitor DIP switch may be transferred into the nonvolatile memory circuit by the user manually operating a code transfer switch. Because the user can change the setting on the DIP switch after transferring the tuning code, Carney""s disclosure solves the problem of an intruder gaining control of the self-contained monitor by simply observing its DIP switch setting and using the same on an unauthorized remote controller. However, in this disclosure, Carney does not teach a means by which to control the system with other than a fixed frequency RF signal and does not solve the problem of momentary power interruptions causing false intrusion reports.
U.S. patent application, Ser. No. 09/624,513 filed Jul. 24, 2000 by William P. Carney, the applicant of the present invention, is a CIP of his above referenced U.S. Pat. No. 6,137,405. In Ser. No. 09/624,513, Carney discloses an improved intrusion detection system similar to that disclosed in its parent case U.S. Pat. No. 6,137,405 summarized above. Further, in application Ser. No. 09/624,513, Carney teaches a short term energy storage circuit which provides secondary power to a volatile memory circuit for a predetermined period of time so that a momentary interruption of primary power lasting less than the predetermined period of time is not sensed by the volatile memory circuit. By not sensing and by not recording momentary interruptions, the improved intrusion detection system taught by Carney minimizes the number of false intrusion reports generated as a result of primary power interruptions. Therefore, Carney""s improved system minimizes the number of times a returning occupant will seek help mistakenly believing an intrusion has occurred as a result of a false intrusion report. However, in this disclosure, Carney does not teach a means by which to control an intrusion detection system with an RF signal other than a fixed frequency RF signal in order to make it difficult for an intruder to intercept the RF signal and duplicate the same to gain control of the system and possibly cause harm to an unsuspecting returning occupant.
As can be seen from the foregoing, there exists a definite need in the art for a self-contained monitor which includes a reliable means by which to record and test for an intrusion event, which generates a minimum number of false intrusion reports due to primary power interruptions and, in addition, employs an RF signal that cannot be easily intercepted and duplicated so that an intruder can gain control of the system and jeopardize the well being of a returning occupant.
The present invention is directed to a system which includes a reliable means by which to record and test for an intrusion event, a system which generates a minimum number of false intrusion reports due to primary power interruptions and, in addition, employs an RF signal that cannot be easily intercepted and duplicated thereby preventing an intruder from gaining control of the system and jeopardizing the well being of a returning occupant.
A first embodiment of the present invention comprises a self-contained monitor which is energized by a primary power source and which is responsive to an authorized remote controller transmitting a particular RF carrier signal under the control of a user. The self-contained monitor includes a nonvolatile memory circuit for storing a tuning code therein, a tuning code circuit for inputting the tuning code communicating with the nonvolatile memory circuit, a transfer switch communicating with the nonvolatile memory circuit and with the tuning code circuit, an RF receiver circuit communicating with a motion detector, a volatile memory circuit, a responder, and with the nonvolatile memory circuit. The motion detector surveils a predetermined space for the presence of an intruder. The transfer switch is manually activated by the user transferring the tuning code from the tuning code circuit to the nonvolatile memory circuit. The RF receiver circuit is made responsive to the particular RF carrier signal by the tuning code stored in the nonvolatile memory circuit. The volatile memory circuit selectively defines an armed state and a disarmed state. The volatile memory circuit is selectively disarmed by either sensing an interruption of primary power or by the motion detector detecting the intruder. The responder is prompted by the RF receiver circuit responding to the particular RF carrier signal to generate a response or absence thereof indicating one of the states of the volatile memory circuit. The remote controller further comprises a DIP switch and the user manually inputs a code setting thereon representing a binary code defining the tuning code which is transmitted as part of the particular RF carrier signal. The tuning code circuit further comprises a plurality of switches. The user manually inputs the code setting thereon and activates the transfer switch thereby storing the tuning code in the nonvolatile memory circuit for subsequently qualifying the particular RF carrier signal transmitted by the remote controller.
A second embodiment of the present invention comprises a second self-contained monitor which is energized by a primary power source and which is responsive to a second authorized remote controller transmitting a second particular RF carrier signal under the control of a user. The second self-contained monitor includes a nonvolatile memory circuit for storing a second tuning code therein, a second tuning code circuit for inputting the second tuning code communicating with the nonvolatile memory circuit, a transfer switch communicating with the nonvolatile memory circuit and with the second tuning code circuit, an RF receiver circuit communicating with a motion detector, a volatile memory circuit, a responder, and with the nonvolatile memory circuit. The motion detector surveils a predetermined space for the presence of an intruder. The transfer switch is manually activated by the user transferring the second tuning code from the second tuning code circuit to the nonvolatile memory circuit. The RF receiver circuit is made responsive to the second particular RF carrier signal by the second tuning code stored in the nonvolatile memory circuit. The volatile memory circuit selectively defines an armed state and a disarmed state. The volatile memory circuit is selectively disarmed by sensing either an interruption of primary power or the motion detector detecting the intruder. The responder is prompted by the RF receiver circuit responding to the second particular RF carrier signal to generate a response or absence thereof indicating one of the states of the volatile memory circuit. The second remote controller further comprises an encoder chip encoding the second particular RF carrier signal with an identification code defining the second tuning code which is transmitted as part of the second particular RF carrier signal. The second tuning code circuit further comprises a decoder chip for decoding the second particular RF carrier signal. The decoder chip is prompted to extract the identification code from the second particular RF carrier signal during a time period wherein the second particular RF carrier signal is being transmitted and simultaneously the transfer switch is being activated to transfer the identification code into the nonvolatile memory circuit for subsequently qualifying the second particular RF carrier signal transmitted by the second remote controller.
A third embodiment of the present invention comprises a third self-contained monitor energized by a primary power source responsive to a third remote controller transmitting a third particular RF carrier signal under the control of a user. The third self-contained monitor includes a microcontroller communicating with a third tuning code circuit for inputting a third tuning code, a transfer switch communicating with the microcontroller and the third tuning code circuit, an RF receiver circuit communicating with a motion detector and with the microcontroller. The motion detector surveils a predetermined space for the presence of an intruder. The transfer switch is manually activated by the user transferring the third tuning code from the third tuning code circuit to the microcontroller. The microcontroller is programmed to define an emulated volatile memory circuit having an armed state and a disarmed state and is programmed to define an emulated nonvolatile memory circuit for storing the tuning code therein. The RF receiver circuit is made responsive to the third particular RF carrier signal by the third tuning code stored in the emulated nonvolatile memory circuit. The third tuning code includes either a binary code or an identification code. The emulated volatile memory circuit is selectively disarmed by either sensing an interruption of primary power or by the motion detector detecting the intruder. The third self-contained monitor further comprises a clock circuit communicating with the emulated volatile memory circuit such that the emulated volatile memory circuit is not switched to the disarmed state by an interruption in primary power lasting less than a preset period of time as measured by the clock circuit.